The present invention relates to a vehicle power supply outlet for receiving, for example, a car cigarette lighter and an electrical device plug.
In the prior art, a vehicle power supply outlet is used to receive a car cigarette lighter. The power supply outlet includes a socket into which the cigarette lighter is inserted. The socket is cylindrical and has a closed bottom surface. Further, the socket is accommodated in a cylindrical case, which is arranged in the instrument panel of a vehicle. A U-shaped bimetal contact is fixed to the inner bottom surface of the socket.
The cigarette lighter includes a handle, which is held by a person's hand, and a lighter main body, which supports the handle. The lighter main body includes an outer body, an inner body, a spring, and a heating element. The outer body and the inner body are cylindrical. A spring is arranged between the outer body and the inner body. When the cigarette lighter is inserted into the socket, the outer body is fixed relative to the socket, and the inner body is movable relative to the outer body from a predetermined position. The spring constantly urges the inner body in a direction in which the inner body returns to its original position, or the predetermined position. The handle is pushed to compress the spring so that the heating element projects from the distal end of the cigarette lighter.
The socket has a circumferential wall. A slot extends through the circumferential wall in the insertion direction of the cigarette lighter. An elastic engagement plate extends through the slot. When the cigarette lighter is inserted into the socket, the cigarette lighter engages and elastically deforms the engagement plate in a radially outward direction of the socket. When the cigarette lighter is completely inserted into the socket, the engagement plate restores its original shape and engages an engagement portion formed in the outer body of the cigarette lighter. In this state, the cigarette lighter is arranged at a position where the cigarette lighter is normally held in the power supply outlet, or a normal position.
To use the vehicle power supply outlet, the handle of the cigarette lighter is pushed in with the cigarette lighter held at the normal position by the engagement plate of the socket. In this state, the outer body of the cigarette lighter is supported in a fixed state by the socket. Thus, only the inner body moves inward as it compresses the spring. This engages the heating element of the cigarette lighter with the bimetal contact. As a result, current flows through and heats the heating element. As the temperature of the heating element increases, the bimetal contact deforms away from the socket. This disengages the heating element from the bimetal. Further, the force of the spring causes the inner body to return to its original position together with the handle. In this state, the outer body of the cigarette lighter is held and supported by the engagement plate of the socket. Thus, the inner body is supported in a state in which the cigarette lighter is arranged at the normal position. The cigarette lighter, in which the heating element has been heated, is then removed from the socket to, for example, light a cigarette (refer to Japanese Laid-Open Patent Publication No. 2004-36995).
In recent years, proposals have been made to use the vehicle power supply outlet to power electrical devices in addition to heating cigarette lighters. For example, a vehicle power supply outlet may be used to power a car navigation system or to charge the battery of a cellular phone. Such an electrical device is provided with a plug, which is inserted into the vehicle power supply outlet. The plug includes a negative terminal, which is urged radially outward to be extensible from the plug, and a positive terminal, which is arranged on the distal end of the plug. When the negative terminal contacts the inner surface of the socket and the positive terminal contacts the inner bottom surface of the socket, power is supplied from the vehicle battery to the electrical device via the plug.
However, the socket has an inner diameter that differs between manufacturers. Thus, the extensible negative terminal of the electrical device plug extends radially outward from the plug in accordance with the inner diameter of the socket. This makes the plug applicable to socket bodies of different inner diameters. Further, the negative terminal of such a plug must contact the inner surface of the socket with a certain level of pressure. Thus, the negative terminal is urged radially outward from the socket by a relatively strong force. However, when the negative terminal engages the engagement plate of the socket, the strong urging force of the negative terminal may deform the engagement plate beyond its elastic deformation limit and permanently bend the engagement plate. If the engagement plate is deformed in such a manner, the next time the cigarette lighter is inserted into the socket, the socket may not be capable of firmly holding the cigarette lighter.